1. Field of the Invention
This invention relates to a coupling device for a limb prosthesis, and more particularly to a magnetic coupling device for connecting a residual limb liner to a residual limb socket of a limb prosthesis, which is applicable for lower limb prosthesis as well as for upper limb prosthesis.
2. Description of Related Arts
Lower limb prosthetics are artificial devices designed to replace the function or appearance of all or a part of the missing lower limb. In contrast, lower limb orthotic devices are designed to support, supplement, or augment the function of an existing lower limb.
All types of lower limb prosthesis include a foot and socket. The socket is part of the prosthesis that connects to the stump. The stump is the end of the lower limb. A pylon is a tube connecting the socket to the foot. A pylon may be used to transfer body weight from the socket to the foot. A suspension system or a coupling system is required for a limb prosthesis to suspend a prosthetic limb from a residual limb for extending to the ground to provide body support, to prevent prosthesis from falling off, as well as to avoid pistoning, and to minimize shear forces on the skin of the amputation limb.
There are various suspension systems or coupling devices that are available in the industry. For instance, a shuttle lock which provides rigid attachment of the liner to the socket and lower leg components, or a suction suspension liner with hypobaric sealing membrane around the silicone liner without an external sleeve or shuttle lock to increase surface contact with the socket wall.
Some of the suspension systems in prior arts utilise suction by venting air from between the residual limb and the socket part during insertion of the limb and is prevented from re-entering through the socket part to maintain the vacuum. For instance, disclosed in U.S. Pat. No. 7,947,085 B2 is a prosthetic device utilizing electric vacuum pump for evacuating the socket of a prosthetic limb, and prosthetic limb system employing such vacuum devices. The prosthetic device comprises a prosthetic socket adapted to receive a residual limb, a vacuum passageway through said prosthetic socket, and an evacuation device comprising an electrically powered vacuum pump and a source of electric power.
Another prior art relates to a suspension/alignment for prosthetic limbs is disclosed in U.S. Pat. No. 6,063,125. Said prosthetic limb suspension system relates to a distal adaptor incorporating an air valve, or a simplified distal adaptor for use with thermoplastic sockets. Also disclosed in U.S. Pat. No. 6,267,787 is a prosthetic attachment locking assembly having prosthetic attachment lock which locks a residual limb stump to a prosthetic limb. Another similar art disclosed in U.S. Pat. No. 7,083,654 is a prosthetic angled locking coupler device for connecting a residual limb socket to a lower limb prosthesis.
The existing systems, however, suffer from a number of shortcomings. One is that the system may result in distal tissue stretching, and pistoning of the prosthesis. This can cause permanent elongation of distal tissue and augment pistoning. Furthermore, the use of the systems may lead to pain, particularly along the tibial crest and cut end of the tibia among transtibial amputees and cut end of the femur among transfemoral amputees. Some patients may experience problem when aligning pin with the plunger pin hole or disengaging pin from the pin lock, particularly to the patients with poor flexibility, strength, and/or manual dexterity, thus causing difficulty and dissatisfaction among the amputees, and raise the problem of aligning and adjusting the liner to the socket.
Also, the complex design of the suspension system renders high cost and time consumption, as well as system failure or improper function due to the accumulation of dust, dirt and other debris within the system. In addition, the donning and doffing problems may arise if the configuration of the systems is complicated.
Accordingly, it can be seen in the prior arts that there exists a need to provide a coupling device for connecting a residual limb liner to a residual limb socket of a limb prosthesis which is simple and easy to be used by amputees, as well as to provide a system to overcome the existing problems.